Interaction of arylazido-beta-alanyl NADP+, a photoaffinity analogue of NADP+, with mitochondrial dihydronicotinamide adenine dinucleotide-ubiquinone reductase.

The abbreviations used are: arylazido-P-alanyl NAD', AY-0-(3-toaffinity analogue of NAD', has been shown to be an active site-labeling reagent for the pyridine nucleotide reactive sites of the NADH-CoQI reductase and the NADH-AcPyAD' transhydrogenase activities present in Complex I.The results of this work suggest the presence of three pyridine nucleotide reactive sites in Complex I, i e .those for NAD(P)H oxidoreductase, NADH-AcPyAD' transhydrogenase, and NADPH-AcPyAD+ transhydrogenase activities.In addition to arylazido-P-alanyl NAD' the NADP+ analogue, arylazido-/?-alanylNADP', a potential photoaffinity analogue for some NADP'-dependent enzymes, has been prepared and utilized in a study of the pyridine nucleotide reactive sites in the NADH-CoQ reductase preparation.Its structural properties and reactivity with the pyridine nucleotidedependent activities present in Complex I are the subject of this communication.